p394fig11.33 The Kaufman stereogram also creates a percept of simultaneous fusion and rivalry.  The square in depth remains fused and the perpendicular lines in the two images are pervceived as rivalrous.<BR>||  3D groupings determine perceived depth, stereogram (Kaufman 1974).  Vertical illusory contours are at different disparities than those of bounding squares.  Illusory square is seen in depth.  Vertical illusory contours are binocularly fused and determine the perceived depth of the square.  Thin, oblique lines, being perpendicular, are rivalrous: simultaneous fusion and rivalry.